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Discussion Starter · #1 ·
My 2015 z4 threw P0456 code. Already replaced purge valve and gas cap. Decided to stop buying parts I didn’t need. Built a smoke drive and ran a smoke test. Smoke is coming out this vent pipe when engine running and not. I sealed it off and confirmed smoke did not come out elsewhere. Since smoke is bellowing out the vent it makes me think it’s not doing it’s job. Appreciate your thoughts.
 

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Discussion Starter · #2 ·
I am feeding smoke in from the white tube which May be wrong. Guessing I need to feed inbound on the pump tube. Definitely no leaks at gas gap or other tubes going back to tank so probably worth the test.
 

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I figured out that the hose in the picture is from the dust filter. I covered it which is a decent test to see if I have a leak at the pump. No smoke showed up at the pump. I am going to smoke test from the pump back to the front of the car.
 

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Looks like I am communicating with myself on this one. Lots of posts on this forum with the same problem but nothing many answers. So, for you people in the future I will share what I figured out. This is a great video I found that does a great job buddy explaining the system. The key to the smoke test is closing the valve. That should seal the vent that I saw smoke coming out in my pic.
Stay tuned…
 

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Discussion Starter · #5 ·
I installed a small wire in the green/black wire on the plug for the pump. Then I grounded the wire and I could hear the vent pipe close. At this point the system is closed so I could perform the smoke test. I removed the hose that connects the purge valve in the front of the car to the white vent tube. The white tube runs back to the pump. I inserted the smoke tube into white tube and looked for smoke at pump, gas cap, and fuel pump in gas tank. Loosened the gas cap and see smoke so I confirmed the system is full of smoke. Did not see any smoke when system is closed.

Reconnected the front hose and disconnected the hose on the filter by the pump and inserted smoke line. Wanted to test all the way back to purge valve and put more smoke at the rear of the car. Did not see any smoke.

I did notice that the o-rings were dry so I cleaned all of them and sprayed light weight oil on each of them.

I am going to reset the error code and drive it. Maybe it’s fixed or maybe it’s not. If not, I will probably replace all the o-rings. That won’t be too complicated of a job. After that probably the pump.

I have seen online that a fuel pump leak does not show a lot of smoke. I am suspect of that but don’t see or smell fuel.

Stay tuned. Feel like Will Smith The Legend when he does his daily announcement over the radio. 😀
 
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